1. Field of Invention
The present invention relates to axial flow type combines and, more particularly, is directed to an improved concave structure used in such combines. While, the improved concave structure is disclosed herein in connection with an axial flow combine of the type having two side-by-side threshing and separating mechanisms, it is to be understood that the improved concave structure is equally applicable to an axial flow combine of the type having only one threshing and separating mechanism.
2. Description of the Prior Art
In an axial flow type combine, the threshing and separating mechanism includes a rotor and an associated concave which each extends axially in the direction of movement of the combine across the field. The crop material is fed into the front end of the mechanism, whereupon the rotor circumferentially sweeps the incoming crop material so as to move the material across the concave several times during the threshing and separating operation. This type of motion makes it imperative that grain threshed from the material be discharged through the concave as soon as possible to prevent any kernel damage. To do this, it is necessary to eliminate any clogging of the concave by unthreshed crop material.
It has been noted that in situations where either the crop material is damp or in high moisture corn conditions, conventional type concaves clog, thereby preventing the grain from being effectively removed from the incoming crop. Concave clogging occurs when the crop adheres to a portion of the concave so as to obstruct the openings contained in the concave. This clogging of the concave causes kernel damage in some crop conditions, especially high moisture corn, and also creates an uneven distribution of material across the cleaning system which adversely effects the overall effectiveness of the cleaning operation of the combine.
The problem of the concave clogging was alleviated to some extent by the structure proposed in U.S. Pat. No. 3,927,678, that being the addition of rollers to the curved transversely extending wires. As disclosed therein, the concave included a number of longitudinally extending bars supported on a number of rib members, with a series of removable curved wires transversely extending through the longitudinal bars to form a grate-like structure. Removable rollers were inserted over the transversely extending curved wires to assist in the movement of crop material over and through the concave.
However, it has been found that the structure disclosed in the aforesaid patent does not provide the optimum solution to the concave clogging problem under all crop conditions.